Injection moulds are used for production of components by injecting under pressure a melt of e.g. plastic into a cavity defined by mould halves. The temperature of the melt depends on the material involved and is transferred to the mould. This heat must be removed for the injection moulded component to obtain a temperature that allows it to be ejected from the mould and handled without dimensional changes. By the production rate being as a rule very high, it is desirable to achieve rapid tempering.
However, mould tempering must take place with great accuracy since plastic shrinks while cooling. If tempering takes place irregularly over the component, dimensional changes in the form of e.g. warping may occur. Warping may be very difficult to predict when components of an essentially three-dimensional extent are involved, i.e. components having an extent other than substantially plane. Irregular tempering may also result in unsatisfactory finish, which is devastating in connection with certain consumer products, such as casings for mobile phones. Therefore the mould designer must, when designing the system for mould tempering, take the geometry and wall thickness of the component into consideration since thicker sections may require additional tempering.
Injection moulds tend to be more and more complex, which in turn increases the problems in connection with mould tempering. Except for the cases where very simple components are involved, such as essentially two-dimensional, mould tempering is always a matter of compromising. The larger and more complex the component the larger amount of material to be tempered. Moreover, complex components require in most cases also a large number of ejectors and slider mechanisms, which all require space in the mould half.
Injection moulds comprise in their simplest embodiment two mould halves which jointly define a cavity. At least one mould half usually comprises a number of ejectors which are arranged in through channels. Moreover, one or more movable sliders are often involved which are also accommodated in the mould half. Thus the mould half is penetrated by a number of channels and recesses. Of course, mould tempering should take place as close as possible to the cavity, which traditionally is solved by drilling a number of through channels in the mould half. Then the openings of the channels are plugged up in such manner that the channels jointly form a network with two open ends. This network can then be connected to a system for circulation, for instance, of a coolant. When a component of three-dimensional extent is involved, such channels must be arranged in several planes in the mould half. This technique is difficult and often causes unsatisfactory mould tempering since it is very complicated or even impossible to vary the geometry of the channels in order to adjust the geometry to the specific need for tempering of different sections of the component. Consequently mould tempering cannot be made optimal. It is also a time-consuming job for the mould maker to drill and plug the mould. There is thus a great need for simple and easy mould tempering for injection moulds for producing components of a substantially three-dimensional extent.